There is widespread use of radioactively labeled biological molecules in research, medicine, industry and for environmental testing. For example, a variety of assays employing radiolabled biological molecules are used in biological research and medicine. For instance, there are many different types of immunoassays used in clinical laboratories and in research. There are also a many clinical assays and research procedures using radioactively labeled nucleic acids. A number of different isotopes are used in these different applications including .sup.14 C, .sup.3 H, .sup.125 I, .sup.131 I, .sup.32 P and .sup.57 Co.
Many of the assays using radioactively labeled biological molecules generate relatively large volumes of low level radioactive waste, which then become a disposal problem. For example, in a typical radioimmunoassay procedure, small amounts of radioactively-labeled material are dispersed into liters of aqueous or organic solutions. These solutions often contain relatively low levels of radioactivity, but nonetheless must be disposed of as radioactive waste according to federal and state regulations.
Disposal of large volumes of low level radioactive liquid waste generated by radioimmunoassays and other procedures is particularly expensive and difficult. Transportation of radioactive waste materials to federal waste disposal sites has become increasingly difficult and expensive. Disposal of low level liquid radioactive waste by transportation to radioactive waste disposal sites is also an inefficient use of space at these sites. Therefore, most institutions try to reduce or eliminate disposal of radioactive waste by this method.
An additional method of radioactive waste disposal involves storing the radioactive waste material on site until the material is no longer radioactive. Fortunately, some of the most commonly used radioisotopes, such as .sup.125 I and .sup.57 Co, have relatively short halflives. Because of this, some institutions store radioactive waste containing such isotopes until the waste is no longer radioactive, and then dispose of the waste as nonradioactive material. However, it is difficult to store large volumes of low level radioactive liquid waste for a period of months or years.
There is a need for methods to remove the radioactively labeled biological molecules in concentrated form from liquid radioactive waste solutions. If this can be accomplished, the concentrated radioactively labeled biological molecules can then more feasibly be stored on site until the radioactivity decays and the waste becomes nonradioactive. Alternatively, the amount of radioactive waste material that must be transported to a radioactive waste disposal site can be dramatically reduced. In either case, the expense associated with liquid radioactive waste disposal can be markedly decreased.